Add a Config::set_once() function to set a value once (and let Config::merge() overwrite it later
Add a Config::set_once() function to set a value once (and let Config::merge() overwrite it later

Signed-off-by: Matthias Beyer <1d6e1cf70ec6f9ab28d3ea4b27a49a77654d370e@beyermatthias.de>

mehcode/config-rs